Today's Word of the Day means...
A soft, white, gray, or yellow limestone consisting mainly of calcium carbonate and formed primarily from the accumulation of fossil microorganisms such as foraminifera and calcareous algae. Chalk is used in making lime, cement, and fertilizers, and as a whitening pigment in ceramics, paints, and cosmetics. The chalk used in classrooms is usually artificial.
A horse favored to win
[1950s+ Horse racing; References to winning by a long chalk, an allusion to scoring points by a chalk mark, date from the 1830s]